The Epidemic Intelligence Service (EIS) of the Centers for Disease Control and Prevention (CDC) is a unique 2-year postgraduate program of service and on-the-job training for health professionals interested in epidemiology. Since 1951, approximately 2600 EIS officers—CDC’s “disease detectives”—have graduated from the program. In addition to the training gained through investigating disease outbreaks, natural and man-made disasters, and other public health emergencies, the program provides formal instruction to its trainees through courses in epidemiology, biostatistics, public health ethics and law, evaluation of surveillance systems, scientific writing, and prevention effectiveness. The 2-fold mission of EIS is training and service. One of the many ways that EIS delivers on its service mission is by forming the backbone of CDC’s ready-response capability. When CDC is called upon to furnish epidemiologic assistance to our public health partners both domestically and internationally, an EIS officer is often the first one dispatched to the site.